2001 Yamaha YZ125(N)/LC Owner's Service Manual PDF (P/N 5MV-28199-30)

This Yamaha Owner's Service Manual, document 5MV-28199-30 (first edition June 2000), covers the 2001 YZ125(N)/LC family and the regional variants listed above. Its seven chapters address operation, race maintenance, engine and chassis repair, electrical troubleshooting, and tuning.

• Engine and transmission: Engine removal, cylinder and piston inspection, crankcase separation, crankshaft installation, clutch service, and transmission disassembly and assembly.

• Carburetor and intake: Mikuni TMXχ38SS carburetor disassembly, fuel-level measurement, reed-valve inspection, and regional jetting and jet-needle setting information.

• Cooling system: Radiator removal, cap-pressure and cooling-system tests, plus water-pump impeller, shaft, bearing, and oil-seal service.

• Brakes and chassis: Caliper and master-cylinder repair, brake bleeding, front-fork overhaul, steering-head service, and swingarm and rear-shock mounting work.

• Ignition diagnosis: Wiring and cable-routing diagrams, ignition fault-finding charts, spark testing, engine-stop switch checks, and ignition-coil and CDI magneto measurements.

• Race preparation and tuning: Maintenance schedules, component break-in procedures, carburetor troubleshooting, sprocket selection, and front and rear suspension setting charts.

The operating sections address owners, while the internal repair procedures suit mechanically experienced readers with the specified service tools and measuring equipment.

Engine, Clutch, and Transmission Repair

Cylinder inspection goes beyond general wear checks: the manual provides piston-to-cylinder clearance data and a matching chart linking cylinder marks to piston sizes and color marks. That chart helps identify the appropriate piston before replacement parts are selected.

Clutch inspection covers the housing, boss, friction plates, springs, and primary driven gear. Transmission procedures address gear engagement surfaces, the shift cam, shift forks, guide bars, and assembly checks. Power-valve and YPVS governor disassembly and installation are covered separately.

Exploded assembly views, sectional illustrations, and job instruction charts accompany the repair procedures. The condition-to-action format connects inspection findings with the specified repair or replacement action. Crankcase separation calls for tool YU-1135-A/90890-01135 and separating bolt YM-1305/90890-01305.

Carburetor Inspection and Regional Tuning

Fuel-system inspection includes the needle valve and seat, throttle-valve movement, fuel level, reed-valve bending, and stopper height. The carburetor instructions expressly exclude disassembly of the venturi block and main nozzle.

Separate jet-needle tables distinguish European settings from the other documented markets. Throttle-opening charts show which setting parts influence each operating range, while symptom-based tables address poor acceleration, plug fouling, and irregular running. Optional setting parts are listed with their part numbers.

Radiator and Water-Pump Service

Cooling coverage combines radiator-cap and system-pressure tests with hose inspection, radiator removal, and coolant replacement data. Water-pump procedures cover the impeller shaft, drive gear, bearings, and seal installation, including the checks associated with coolant loss or milky transmission oil.

Brake, Fork, and Rear-Suspension Work

Brake coverage includes piston and seal inspection, master-cylinder assembly, hose routing, and bleeding. Wheel-bearing replacement and steering-head inspection support the chassis work.

Front-fork procedures cover the damper rod, base valve, bushings, oil seals, oil-level setting, and damping adjustments. Yamaha recommends dealer maintenance for the fork. The assembly notes warn that a dropped damper rod can damage the internal valve.

The swingarm section covers linkage bearings and seals and warns that incorrect connecting-rod nut placement can cause contact with the swingarm during suspension compression.

Rear-shock scope: Removal, spring and mounting-bearing service, preload adjustment, and installation are included. The manual prohibits disassembly of the nitrogen-charged cylinder and reservoir; it specifies assembly replacement for oil or gas leakage. Its pressure-related handling warnings remain relevant to this work.

Suspension setting charts connect handling symptoms with spring selection, damping adjustments, and fork oil level, with separate regional baseline settings.

Ignition Testing and Wiring References

The Electrical Components and Wiring Diagram section identifies the ignition components and wire colors. Cable Routing Diagrams document harness, control-cable, and hose placement.

The ignition inspection flowchart links a no-spark complaint to connection checks, the engine-stop switch, ignition coil, and CDI magneto. Test illustrations show the relevant connector positions and meter connections, supporting fault isolation before the CDI unit is considered for replacement.

A Preview of Engine Torque and Ignition Test Data

These examples represent a small selection of the manual's component-specific tightening and electrical inspection data.

The engine tables list 28 Nm for the cylinder-head nuts, accompanied by staged, crisscross tightening instructions, and 80 Nm for the clutch-boss nut.

For ignition diagnosis, the CDI magneto pickup-coil specification is 248–372 ohms at 20°C (68°F), measured between the white/red and white/blue leads. The electrical chapter pairs this specification with connector illustrations.

Searchable Text, Contents Bookmarks, and PDF Layout

Search and diagram detail: The main text is searchable, although labels embedded in some drawings are not captured by text search. Embedded bookmarks lead to the relevant contents pages rather than directly to chapter openings. Small wiring and connector labels are readable when enlarged.

The download contains one printable, 558-page PDF in English, French, German, and Italian. This is one multilingual publication. The total already includes the front and back covers, two memo pages, and one blank page.